import java.util.Stack;

public class Solution {
    public boolean isValid(String s){
//        Stack<Character> stack = new Stack<>();
        ArrayStack<Character> stack = new ArrayStack<>();
        for(int i = 0;i < s.length();i++){
            char c = s.charAt(i);
            if(c == '(' || c == '[' || c == '{')
                stack.push(c);
            else{
                if(stack.isEmpty())
                    return false;
                char topChar = stack.pop();
                if(c == ')' && topChar != '(')
                    return false;
                if(c == ']' && topChar != '[')
                    return false;
                if(c == '}' && topChar != '{')
                    return false;
            }
        }
        return stack.isEmpty();
    }

    public static void main(String[] args) {
        System.out.println(new Solution().isValid("()[]{}"));
        System.out.println(new Solution().isValid("([)]"));
    }
}
